1. Field of the Invention
The present invention relates to a vehicle safety running apparatus for a vehicle provided with a so-called navigation system, and more particularly to a vehicle safety running apparatus for allowing a subject vehicle to pass through intersections and curves in front thereof exactly even when a route to a destination is not set.
2. Description of the Related Art
A Japanese Patent Unexamined Publication No. Hei. 8-194896(JP-A-8-194896) describes a safety running apparatus for preventing the execution of improper automatic deceleration or alarming the driver when the driver does not follow a route guidance at intersections by excluding them from objects for control in a case where vehicle speed control and/or alarming is executed according to the shapes of curves coming up in front of a subject vehicle along a road on which the subject vehicle is traveling while a route guidance by a navigation system is being carried out.
In addition, a Japanese Patent Unexamined Publication No. Hei. 7-229745(JP-A-7-229745) discloses a safety running apparatus for executing automatic deceleration control and alarming against a route to be taken by a subject vehicle after the subject vehicle deviates from its route by alarming the driver in the event that the subject vehicle deviates from its route or a deviation of the subject vehicle from its route is anticipated while a route guidance by a navigation system is being carried out.
In order to execute proper automatic deceleration control and alarming for a subject vehicle to securely pass along a road in front thereof the driver is required to grasp the shapes of roads based on a future route for him or her to take. To this end, conventionally, while a route guidance by a navigation system is being carried out and in a case where a route that will be followed by the subject vehicle in the future can be anticipated, the automatic deceleration control and/or alarming is carried out based on the shapes of roads along a set route. However, there occurs a case where the route guidance by the navigation system is not executed on roads that are used very frequently or are known to the driver. Alternatively, there occurs a case where the subject vehicle deviates its route even when the route guidance is being carried out, and in such a case, the conventional safety running apparatus has faced a problem that it cannot execute precise vehicle speed control and alarming.
In order to improve the safety in driving the subject vehicle when the route guidance by the navigation system is not in operation, it is considered to select a branch road which is the most difficult for the subject vehicle to pass through such as a branch road having a largest intersection angle relative to a road on which the subject vehicle is running or a branch road having a curve having a smallest radius of curvature and then to control the vehicle speed or alarm the driver so that the subject vehicle can pass through the branch road safely. However, with such a system in operation, even in the event that the subject vehicle enters a branch road which is not the branch road so selected, the control or alarming is still activated and it follows that the unnecessary control or alarming is executed. Thus, the driver may feel uncomfortable.
The invention was made in view of these situations, and an object thereof is to enable the precise execution of controlling the vehicle speed and alarming the driver according to the shape of a road ahead of the subject vehicle.
With a view to attaining the object, according to a first aspect of the invention, there is provided a vehicle safety running apparatus comprising a storage means for storing road data including intersections and a subject vehicle position detecting means for detecting the position of a subject vehicle, a route setting means for setting a route to a destination, a vehicle condition detecting means for detecting the vehicle condition of the subject vehicle including at least the vehicle speed thereof, a bend portion detecting means for detecting curves and intersections existing along the traveling direction of the subject vehicle based on the road data stored in the storage means and the subject vehicle position detected by the subject vehicle position detecting means and a proper condition determining means for calculating, based on information on curves and intersections detected by the bend portion detecting means proper vehicle conditions for passing through the curves and intersections and determining whether or not the subject vehicle can properly pass through the curves and intersections based on the result of a comparison of the proper vehicle condition so calculated with the vehicle condition detected by the vehicle condition detecting means; the vehicle safety running apparatus further comprising a running difficulty determining means for determining the degree of difficulty in running on a road on which the subject vehicle is traveling, whereby when the bend portion detecting means detects an intersection branching into a plurality of branch roads in a state in which a route guidance based on a set route is not carried out, the proper condition determining means selects a branch road determined by the running difficulty determining means as having a lowest degree of difficulty in running and determining whether or not the subject vehicle can pass through the branch road.
According to the configuration as described above, since a branch road of branch roads at an intersection ahead of the subject vehicle along a road on which the subject vehicle is traveling which has the lowest degree of difficulty in running is selected to determine whether or not the subject vehicle can pass therethrough in the state in which the route guidance along a set route is not carried out, it is possible to determine whether or not the subject vehicle can pass through the branch road even in a case where no route to a destination is not set. Moreover, the possibility that automatic deceleration control and/or alarming is performed excessively can be reduced by selecting a branch road which is easy for the subject vehicle to pass through, thereby making it possible to suppress to a minimum level the physical disorder that the driver feels. In addition, even in the event that the subject vehicle happens to enter a branch road which is difficult for the subject vehicle to pass through, since in many cases the driver drives the vehicle without depending on the route guidance when he or she has already been aware of the existence of an intersection ahead of the subject vehicle or is then determined on which turn to take at the intersection, it is most unlikely that the subject vehicle enters the branch road which is difficult for it to pass through with excessive vehicle speed.
Additionally, according to a second aspect of the invention, there is provided a vehicle safety running apparatus as set forth in the first aspect of the invention, wherein the storage means is configured to store road data through nodes and links, and wherein the running difficulty determining means is configured to determine that a branch road having a smaller intersecting angle formed by links immediately before and after a node set at an intersection is lower in the degree of difficulty in running.
According to the configuration as described above, it is possible to determine exactly a branch road having a lowest degree of difficulty in running by selecting a branch road having a smallest intersection angle formed by links located before and after a node set at an intersection.
Furthermore, according to a third aspect of the invention, there is provided a vehicle safety running apparatus as set forth in the first or second aspect of the invention, wherein the proper condition determining means determines whether or not a curve on a branch road selected by the proper condition determining means can be passed along.
According to the configuration as described above, since whether or not the subject vehicle can pass through the selected curve on the branch road is determined, it is possible to perform an accurate automatic deceleration control and/or give an alarm to the driver by determining whether or not a curve along which the subject vehicle is anticipated to pass.
Moreover, according to a fourth aspect of the invention, there is provided a vehicle safety running apparatus as set forth in the third aspect, wherein the proper condition determining means cancels its determination on whether or not the curve on the branch road selected by the proper condition determining means can be passed along when the subject vehicle starts to advance on a branch road other than the branch road selected by the proper condition determining means.
According to the above configuration, when the subject vehicle advances on a branch road other than the selected branch road, since the determination of the passableness of the selected curve on the selected branch road is cancelled, it is possible to prevent the execution of the automatic deceleration control and/or alarming the driver for the curve along which the subject vehicle is passing in no case then.
In addition, according to a fifth aspect of the invention, there is provided a vehicle safety running apparatus as set forth in any of the first to third aspects of the invention, wherein the proper condition determining means cancels its selection of a branch road when direction indicators of the subject vehicle indicate before the intersection that the subject vehicle is advancing on a branch road other than a branch road selected by the proper condition determining means.
According to the above configuration, in a case where a branch road selected by the proper condition determining means is different from a branch road indicated by the direction indicators, since the selection made by the proper condition determining means is cancelled, it is possible to prevent a determination from being made on a curve on a branch road which the subject vehicle enters in no case.
According to a sixth aspect of the invention, there is provided a vehicle safety running apparatus as set forth in any of the first to fifth aspect of the invention, further comprising a route deviation determining means for determining whether or not the subject vehicle deviates from its set route by comparing a route set by the route setting means with a position of the subject vehicle detected by the subject vehicle position detecting means, wherein the state in which a route guidance based on a set route is not carried out involves where a deviation from the set route is detected by the route deviation determining means.
According to the configuration as described above, whether or not a branch road or curve can be passed through is determined not only where no route to a destination is set but also where the subject vehicle deviates from its set route, and moreover, the possibility that automatic deceleration control and/or alarming the driver is performed excessively can be reduced, thereby making it possible to suppress to a minimum level the physical disorder that the driver may feel.